Robotic arms have been in existence for several decades. Many industries utilize robotic arms to speed production, improve product assembly quality, and manipulate hazardous objects and materials. Most robotic arms in the world are designed for heavy, repetitive manufacturing work, and handle tasks that are difficult, dangerous, or boring to human beings.
A typical robotic arm is controlled by a computer by activating individual step motors or actuators connected at each joint. At a minimum, a robotic arm has a single segment and a joint at each end. Larger robotic arms often use hydraulics or pneumatics to control arm motion. Robotic arms often use motion sensors to regulate movement in precise increments.
A robotic arm, called the Shuttle Remote Manipulator System (SRMS) or Canadarm, was used on the Space Shuttle to maneuver a payload from the payload bay of the orbiter to a deployment position and then release the payload. The SRMS is also able to grapple certain payloads, maneuver it to the payload bay of the orbiter, and berth it. SRMS was first used on the second Space Shuttle mission launched Nov. 13, 1981. The SRMS robotic arm is 15.2 meters (50 feet, 3 inches) long and 38 centimeters (15 inches) in diameter, and has six degrees of freedom. It weighs 410 kilograms (905 pounds). Although the original SRMS was capable of deploying or retrieving payloads weighing up to 32.5 tons, the system was later upgraded to increase payload capacity up to 293 tons in order to support space station assembly operations.
A later robotic arm, the Mobile Servicing System (MSS) or Canadarm2, is used on the International Space Station (ISS). Launched to the ISS in 2001, it plays a key role in station assembly and maintenance. The MSS moves equipment and supplies around the station, supports astronauts working in space, and services instruments and payloads attached to the ISS. The MSS is self-relocatable, and can move end-over-end to reach many parts of the ISS. The ISS is planned to also utilize other robotic arms such as the Japanese Experimental Module Remote Manipulator System (JEM-RMS) and the European Robotic Arm (ERA).
Current technology robotic arms utilize capture heads incorporating mechanical grippers, where mechanical force between two or more surfaces are used to positively capture and move objects. Mechanical grippers are suitable to capture known objects of predictable size, shape, and orientation and having robust attachment surfaces.